At the present time, such forming is performed by means of a rod which is pivoted on the machine so as to be able to come and lie in prolongation of the front guiding rail, while a fixed rear plate is located in prolongation of the rear guiding rails. In this way, when the conveyor belt or the conveyor moves forward, the open end of the bag is inserted between the two guiding rails, while being formed by the pivoted rod, on the one hand, and by the rear plate, on the other hand. This known device is disclosed in commonly assigned U.S. Pat. No. 3,896,605 (MBJ-123-A) naming Marcel Chevalier as inventor, the entire disclosure of which is incorporated herein by reference thereto.
This known device has several drawbacks. As a matter of fact, a complicated mechanism must be provided to synchronize the motion of the pivoted rod with the various operating steps. This mechanism must, in particular, after the forward movement of the conveyor, control the falling back of the rod to a vertical position, then the movement of said rod in a forward direction, the raising thereof, and, lastly, the movement of the rod rearwards till said rod lies again in prolongation of the front guiding rail.
The object of the invention is to obviate such drawbacks by providing a forming device which is both simple and inexpensive.